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Mortgage Loans Held for Sale (Details) - USD ($) $ in Millions | Sep. 30, 2018 | Dec. 31, 2017
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Mortgage Loans Held for Sale (Textual) |  |
Mortgage loans held for sale, fair value | $ 9.3 | $ 11.8

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- References No definition available. + Details
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Namespace Prefix: | sfst_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Fair value portion of mortgage loans held-for-sale. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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